Off-shore oil drilling is widely practiced but is subject to concerns about harm to marine life and shoreline beaches, flora, fauna and habitations in the event of oil leakage which can be quite serious ecologically and economically as shown by the 2010 experience in the Gulf of Mexico, as one example.
Drilling techniques have been developed to an extent that allows successful drilling and oil recovery at very deep locations, such as a mile or more from the wellhead to the surface. The oil rig provides for travel of the oil through a pipe or conduit. There is also technology, such as the use of blow-out preventers, for preventing or limiting release of oil into the sea water in the event there is a failure in the structure at the wellhead. However, devices such as blow-out preventers are also subject to mechanical failure and the entire operation of an off-shore drilling rig or platform is subject to some risk of human operator errors that can result in serious leakage.
Such problems can occur in wells at any depth but can be aggravated in very deep water because the distance from the surface and the greater water pressure at such depths prevents or severely limits human and, also, robotic accessibility to the wellhead site. Likewise, those circumstances, combined with the pressure or force of oil discharged from the wellhead, make it difficult to cap or seal the well by massive closed structures or materials lowered from the surface intended to block the escape of any oil.
In addition to escaping oil, there can be massive volumes of gas escaping from the wellhead that is immediately subjected to the high pressure of the deep water plus the very cold temperature prevalent at great depths. These can cause gas, or other substances in the crude oil, to condense or freeze and interfere with passage of the oil through a conduit to the surface even after a closed structure is placed over the wellhead. Consequently, it can be necessary to additionally provide a way to improve recovery of the gases, as well as oil, from the leak site.
Prior efforts to devise leak containment systems have taken account of the well known fact that oil, and gas, from a leak site is normally less dense than sea water and will rise through the water toward the surface. However, it is not believed that prior systems are sufficiently practical in terms of one or more of their characteristics including material costs, the facility with which the necessary apparatus can be put in place, and the ease of confinement and recoverability of the rising oil and gas. The deficiencies of such known prior systems appear particularly to hinder their application in instances of leakages from sites that are quite deep, such as in excess of a mile.
The ultimate recourse is often to drill an auxiliary relief well through the sea floor to the underlying oil deposit to try to relieve pressure from the leaking well. That is a partial remedy, at best, that is quite costly and can take a long time to do.
Any strategies employed to stop or control serious leakage still tend to leave a major risk of harm from the already escaped oil, and that oil is difficult to clean up or recover economically.
Consequently, new techniques for dealing with undersea oil leaks are highly desirable in order to make existing off-shore oil wells less risky and to have better assurance of safety for drilling to occur at additional sites.